The investigative arm of the IRS says that 1.8 million people have reported receiving impostor calls. More than 9,600 victims have been scammed out of more than $50 million.

Phishing and malware incidents rose roughly 400 percent during the 2016 tax filing season. Despite officials’ best efforts to curb the increase, it’s expected that the numbers of tax-related scam attempts will continue to grow.

Increasingly popular with scammers is the robo-call. The crooks leave urgent call-back requests, demanding payment of “back taxes” with gift cards. IRS officials say such demands are clear signs of a scam.

Other callers may ask for payment of a nonexistent “federal student tax.” People they call are told to wire money — another sure sign of a scam — with threats of legal action unless payment comes at once.

Another scheme involves a call saying the IRS “just needs a few details” to speed up the processing of your refund. The scammer tries to get personal information such as Social Security numbers, bank routing numbers or other sensitive data such as credit card numbers.

Human resources and payroll professionals have been targeted as well, through requests for information about employees. A scammer posing as the company’s CEO requests personal and financial information, including Social Security numbers.

In an effort to catch scammers and identity thieves, the IRS is delaying refunds this year for anyone claiming the earned income tax credit (EITC) or the additional child tax credit (ACTC). That move is expected to give the IRS added time to weed out more sophisticated fraudulent returns. It may also hurt lower income taxpayers who file early and likely will be waiting at least until late February for refunds. Offers to “help speed up your refund” may be more scams.

Sen. Susan Collins, R-Maine, chairs the Senate’s Special Committee on Aging, which has published a guidebook on avoiding scams. Read it online at aging.senate.gov/imo/media/doc/217925%20Fraud%20Book%20Final.pdf. You also can call the committee’s fraud hotline (1-855-303-9470) for information or to report fraud attempts.